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HYB: orange

To save some newcomers time spent plowing through the archives:

THE WORLD OF IRIS provides a detailed explanation of the carotenes.  Its 
discussion of chemical pathways gets pretty deep, but the most important 
thing to remember is that this is an entire family of pigments of varying 
colors from yellow through yellow-orange to orange-red.  They can, and do, 
appear both together and separately -- which provides the potential for many 
different shades of yellow and orange.

On page 426, there is a table showing the occurence of these, and other, 
pigments in 28 varieties of TBs.  You may have to consult checklists for some 
you don't recognize, but I found comparing this analysis with photos and 
descriptions to be VERY enlightening.  [Linda -- another of your dreaded 
"homework assignments"!]  

Dr. Werckmeister described these as plastids within the cell wall of the 
epidermal layer and his model does explain why oranges produced by a mixture 
of carotenes appear to be smooth, rather than striated or washed.  If you are 
interested only in TBs, this model is the most useful I've found.  Browns are 
explained as the combination of violet-colored cell sap, seen through the 
yellow plastids in the cell wall -- the depth of the brown depending, of 
course, on the intensity of the violet and yellow components. So:

pale-violet + yellow-orange = deeper orange

This can also explain the pixelated effect found in some arilbreds [and, I 
suspect, in some older TBs] because it treats each cell as a separate entity. 
 PIXILATED is a good example, not a true orange, but on portions of the 
flower the mixture of pink and deep yellow is so intense that it does look 
orange from a distance. Early hybridizers of pink TBs worked so hard to get 
the yellow out of the pink-and-yellow blends that I wonder if some of those 
cultivars did not also have this pixelated pattern. 

Werckmeister's model does not, however, explain the barber-pole effects 
apparent in so many arilbreds.   These have changeable color, depending on 
the angle at which the flower is viewed.  Such oranges are produced by a 
surface layer of reddish-violet overlaying a yellow base.  Some can be as 
intense as the orange of a robin's breast.  

If you include apricots and peaches in the "orange" group, there are even 
more routes to explore -- but I'd rather save than until another day.  

Sharon McAllister

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